cold-water coral research in Sweden  

Welcome to the Guide to all Phyla and the Illustrated Species List
The organisms portrayed in the illustrated species list were sitting on six sets of ceramic tiles (48 in total) deployed at the cold-water coral reef at Saekken, NE Skagerrak. After 5-6 years of deployment at 85 meters depth, this is what was staring back at me when I looked at the tiles through the stereo magnifier. The organisms are grouped by the higher taxonomic ranking phylum (e.g. mollusks, cnidarians, 'moss animals' etc) and the lower rankings (i.e. class, order and family) are displayed as headlines above the images. There is also a complete species list with the higher taxonomic rankings displayed. In the species list you can also see if a specific species is depicted in the illustrated list. In the guide to all phyla you will get a short description of the groups, and the small image next to each phylum is a link to the illustrated species list with a photo gallery of some of the species within this group.


Cold-water corals and associates


UW-photo by Tomas Lundälv. The image was taken with a camera mounted on the ROV (Remote Operated Vehicle, an unmanned submersible).


The complex matrix of coral branches creates turbulence in the water, increasing the fall-out of nutritious particles and larvae within the reef. This is the key to why coral reef habitats are amongst the richest in species diversity and abundance. Most of the species found in coral habitats reflects the local fauna and can be found on other substrates. Of the local species pool four groups were found in much larger numbers close to corals; i.e. sponges (Porifera), crustaceans, bristleworms (Polychaeta, Annelida), and 'moss animals' (Bryozoa). But some organisms are extra tightly linked to the coral habitat and is found almost solely in this type of environment. The true 'coral lovers' are presented below.

The polychaete Eunice norvegica (below to the left) can become 25-30 cm long and builds parchment like tubes along the coral branches. The corals then calcify the tubes, making both the coral branches and the tube stronger. Despite the fierce looking fangs (see the image further down on the page) it is supposed to eat foraminiferans (unicellular protozoans). The odd looking hemichordate Rhabdopleura normani is another organism found solely in coral habitats (images to the right below). The larger image shows the colony with its blood red stolon and perpendicular transparent annulated tubes. In these tubes the individual animal resides, and one of them is seen out of its tube on the bottom right image. The brachiopod Macandrevia cranium (bottom, middle) was a regular catch in samples taken in the Koster Fjord up until the 1970's. But with the decline of coral cover it dissapeared, and is now only found at Saekken. Below you also find a squat lobster (Munidopsis serricornis) that is common in the reefs. In tropical reefs they have found that corals benefit from symbiotic relationships with trapezoid crabs. The crabs act as housekeepers and clean the corals from particles too big for them to shed off, and the crabs benefit by getting a safe foraging area between branches. Studies shows that transplanted corals with crabs have better survival than corals without. Munidopsis could be the housekeepers of Lophelia reefs. This type of win-win relationship amongst animals is called mutualistic symbiosis.


Left: Eunice norvegica with extruded fangs. Middle: you often see the claws of the small squat lobster Munidopsis serricornis sticking out between branches of corals. Right: Barentia sp. (Entoprocta) was found almost solely on panels close to corals.


The soft octocoral Alcyonium norvegicum is one of the invertebrates thriving in the stony coral habitat. It was only found on the panels that had been very close to corals. 202 colonies of A. norvegicum were found on the two racks closest to the Lophelia colonies, while only two small ones were found on the four racks standing more than three meters away from the stony corals.

Settling panels


The settling panels consisted of two opposite rows of ceramic tiles mounted on PVC bars. The tiles were c. 10 by 20 cm, one side smooth and one side with grooves. The racks were deployed in January and February 2001, and collected after 5-6 years deployment during 2006 and 2007.


UW-photos by Tomas Lundälv.



Settling panels standing several meters away from any living coral colonies where surprisingly "clean" despite the long residence time and occupied mainly by the feather star Hathrometra sarsii (Crinoidea, left image). Underneath the racks, on the protected sides, there were however a denser population of settled organisms. The feather stars are mobile species attaches only by 'cirri' (jointed feet) and can let go and swim off to settle down elsewhere when disturbed. They ususally occupy any protruding object on the seafloor in this area. Panels standing closer to live coral colonies (right) had much denser colonization and here the exposed sides had large colonies of the colonial serpulids Filograna implexa and Salmacina dysteri. They had settled on the wake side of the panels (according to dominating current direction) and grew over the top of the rack. The brown "fur" on the panels are arborescent foraminiferans, unicellular organisms with a bushy cover of sediment particles. There is also a long arched sediment tube of a peacock worm (Sabella pavonina) and some tunicates visible on the exposed surfaces. A small soft octocoral (Alcyonium norvegicum) and other organisms were also present but too small to be seen on the image. On the image to the right you can see colonies of Lophelia in the background to the right.